diff --git a/SAMv1.tex b/SAMv1.tex
index c1d76d1a..5470b23e 100644
--- a/SAMv1.tex
+++ b/SAMv1.tex
@@ -737,6 +737,7 @@ \section{Recommended Practice for the SAM Format}
   \item Unmapped reads should be stored in the orientation in which they came
     off the sequencing machine and have their {\sf reverse} flag bit~(0x10)
     correspondingly unset.
+  \item Unmapped reads should have mapping quality zero.
   \end{enumerate}
 \item Multiple mapping
   \begin{enumerate}[label=\arabic*]